Horn unit and mounting thereof



March 12, 1940.

L. M. WILEY HORN UNIT AND MOUNTING THEREOF Filed April 16, 1937 2 Sheets-Sheet 1 INVENTOR A66 M 14 176 Y4 A TTORNE Y5.

Patented Mar. 12, 1940 HORN UNIT AND! MOUNTING. THEREOF Lee M. Wiley, Marion, Ind., assignor to Delta Electric Company, Marion, 11111., a corporation of Indiana I Application April 16, 1937, Serial No. 137,221

. l I 10 Claims.-

The present invention relates to electromagnetic horns and means for mounting the same.

One object of the invention is to provide a power unit for a horn of improved construction, which unit is characterized by its small size, compact, simple construction, and which it may be assembled.

Another object of the invention is to provide a horn assembly in which all of the relatively moving parts are fixed in proper spaced relation independently of variationsv in dimensions of the casing.

Another object of the invention is to provide a horn unit in which the maximum possible magthe ease with netic efi'ect and sound is produced by a relatively small electromagnet.

Another object of the invention is to improve the details of constructionof a horn including the circuit interrupter mechanism for the electromagnet and the armature and diaphragm mountings.

Another object of the invention is to providea power unit for a horn which is readily adapted for assembly with diaphragms of different sizes and for mounting in difierent types of casings,

either alone or in conjunction with other instrumentalities, such as a lamp.

horn and lamp in a single casing. I Other objects and advantages of the invention Another object of the invention is to provide an improved and simplified structure combining will become apparent from the following specification, the accompanying drawings,' and the appended claims.

In the drawings: f I Figure 1 is a central longitudinal section through the improved horn'unit;

Fig. 2 is a perspective View of the oup shaped stamping that coil.

' Fig. 3 is a section taken on the line 3-3 of surrounds the electromagnetic Fig. 1;

Fig. 4 is a section taken on the line 44 of I Fig. 1;

Fig. 5 is a section taken on the line 55 of Fig. 4;

Fig. 6 shows the improved horn unit assembled I in conjunction with a diaphragm of larger size than that shown in Fig. 1;

Fig. '7 shows the improved horn unit embodied in a combined horn and light mounted in a single casing; I

Fig. 8 is a longitudinal section through the horn and light unit shown in Fig. 'I;

. casing.

the coil 2!.

(01. 177-7) r I I Fig. 9 is a section taken on the line 9-9 of Fig. 8;

Fig. 10 is a section taken on the line Ill-lot Fig. 11. isa perspective view of the element 5" I utilized to connect the horn and light casings; .and

Fig. 12 is a side elevational'vi'ew of the' completed horn and light unit.

Referring to the drawings; and particularly Fig. 1 thereof, the im'provedhorn unit comprises a casing ill of generally cylindrical form,'having a closed end wall H and being provided at the opposite end with an'outwardly extending flange.

12. The flange I2 is circular except-for a minor projection l3, the purpose of which is setforth hereinafter. I

Mounted within the casing is an electromagnet assembly comprising 'a core piece 'Mjwhich'proI- jects through an opening in and is suppo-rted'iat one end by a disc l5 of insulating material which is of substantially the same externalv configura-'- tion'as the inside of the casing l0.'.The opposite I end'of the core piece I4 is provided with a shoul- "der l6 which seats against theinner-"side of the?" end wall of a cup shaped stamping IT. [This end of the core piece isprovided with a central axiall tubular extensionlli which. projects through an opening in ,the endwallof the cup andis adapted also to project through a correspondingopening in the end wall offthe casing, whereupon it is flanged to lock the core piece and, cup to the- When the core piece is locked to: the casing as described, the edge of the cup shaped stamping seats against the disc I5 and holdsit in properly spaced position with respect to the" end wall I l of the casing Ill. The core piece may in addition beprovided with a tappedholej I9 which maybe used for mounting purposes if desired. I

Positioned upon the core piece I4, within the cup l1 and "adjacent the end wallthereof, is a second insulating disc 20, which, together with disc 15 and the core piece, forms a spool-like structure to confine the electrical coil 2! of the electromagnet.. This coil is shown only as of a few turns for illustrative purposes. Actually it completely fills but does not make contact with the cup I1. I i I An exterior terminal is provided for one endof in 'the disc 15. Onelterminal 24 of thefcoil Zlis' This terminal assembly includes a}- bolt 22 which extends through a suitable opening in. the end wall H of the casingexteriorly' of v the cup I! and through'a corresponding opening nuts are provided upon the projecting extremity of bolt 22 for holding the bolt and the disc IS in position and for securing to the bolt the ex terior electrical wiring. A suitable washer 26 is providedto insulate the bolt 22 from the casing H.

As best shown in Fig. 2, the cup IT is provided with a projection 2'! adapted to extend through a suitableopening, not shown, in the disc l5 to prevent relative rotation of disc and the cup.

Since the cup is locked to the casing by the flanged over projection. it of the core piece it, thispre vents relative rotation of the disc l5 and casing It. The cup is also provided with a struck out tongue 28 which projects in contact with 'the rear face of disc i5 along side of but not touching bolt 22. This tongue supports the edge of the disc l5 against the load applied thereto by the bolt 22 and thereby prevents tilting of the disc with respect to the cup. Preferably the slot 28 from which the tongue 28'is struck is made of greater peripheral length than the length of the tongue in order to provide clearance for the last that no contact occurs between the coil and the turnof the coil 2!. This is advisable to insure cup: Any 'suitable insulating sleeve may be -placed between the coil and the core it, if demovable with respect to the core.

sired. but this is not necessary as the'coil is covered with lacquer and the inner turns are The casing'is also provided with an adjusting screw 39 which is threaded into the end wall H and projects through a suitable opening in the disc-I5 for a purpose to be described hereinafter. A look nut 31 is provided for locking the adjusting screw in any desired position. The power unit per se is completed by a circuit interrupter for the coil2l and a movable armatura which. devices, in the present construction, are supported upon resilient sheet metal plates, indicated genorally at 36 and 31, respectively. When the pow er unitis assembled, these plates are simply seated. against.- the .fiange It. in overlapping relation, with the result that they are properly posi tioned-with respect to each other independently of'the casing.

The armature supporting'plate fill, as best.

one;si de of the hub. .A retaining ring M is then welded or otherwise secured to the cylindrical portion 42 to lock the armature to the spider 3?. Pr eferably the spider is formed of high grade spring steeL. While the spider 3'! may have a continuous annular ring portion 38 connected to each of the spokes 29, it is found that a larger.

volume of sound is produced for a given amount of power if the ring portion 38 is broken, as shown at 45 in Fig. 3, and separated at that point from one of the spokes. The spoke which is separated will be free to move in the direction of its length 'to-permit a greater amplitude of vibration but is still held against flange !2 of the casing so that movements of the armature will be properly guided.

As. shownrbest in Figures! and 5,.the interture 4i. ible-sheet metal is riveted at 58 to one side of the electrically insulated from each other.

manner.

r secured beneath the head of the bolt. Suitable rupter supporting plate 36 comprises an annular portion 36 adapted to seat against'the shoulder E2 of the casing. This annular portion is 'circular except for a minor projection l3 which corresponds in location and size with the projection it on flange 12 of the casing; The interrupter support 36 is further provided with a contact supporting finger in which projects inwardly from the'annular portion lt and-extends in a circular path around" the periphery of the arma A movable contact element 49 of flexfinger il with a layer 55 of insulating material between the element 19' and thefinger ll. A second layer 52 of insulating material is provided between the rivet heads and the element 49, with the result that the element 49 and finger 4'! are of the armature coil 2! is connected to the movable contact element at 53 in any. desired The opposite end of the movable contact member 49 is provided with a projection 56 which extends into the path of movement of the armature ll, with the result that the armature upon movement thereof towards the electromagnet deflects the movable contact member 49 away from the finger 47. It will be noted that as shown in Figure 5 the insulating layer 5| overlies the projection 56 ofthe movable contact ele merit, with the result that the armature makes contact with the insulating layer rather than the metallic portion of projection 56.

The finger 41' and movable contact element.

49 are provided with apair of contact elements 5? and 58, respectively, which are normally in electrically conductive. engagement with each other. For this purpose, the insulating layer. 5|

is provided with a suitable aperture through which contact elements 5? and 58 may make contact. v

One terminal of the exterior electrical circuit is connected to the bolt 22 by means of nuts 25, as previously described, and the other terminal is grounded to the casing Ill. When the external circuit is closed, the current flows from the bolt 22 to the terminal 2 1 of the coil ill, through the coil and the opposite terminal 54' thereof to the movable contact element 49. From that point, if the contact elements 57 and 58 are in engagement, the current flows through such elements to the finger d! and thence to the annular portion d6 of the interrupter support-35, which annular portion is grounded tofthe casing at flange lZ of Such a current energizes the electrothe latter. magnet and draws the armature ll to the left, as viewed in Fig. 1. After a predetermined movement of the armature, it'engages the projection on the movable contact member '39, and deflects the latter to break the circuit at contacts Thereupon the armature is retracted by the inherent resiliency of the spring steel 5'! and 58.

spider element 3? which supports the armature. Upon retraction of the armature, the circuit is The movagain closed at contacts 5'5 and 58 by reason of the inherent resiliency of the movable contact member 49. It is apparent therefore that the armature will oscillate rapidlytowards and from the core of the electromagnet and will continue to do so, so long as the-exterior circuit is closed. The terminals 24 and 541 of coil 2! extend'through suitable openings, not shown; in the disc l5.

The tone oitheJhorn depends upon the period the electromagnet, the stifiness of spider 3T, and

the normal spacing between the armature and projection 56 on the movable contact member 49. The volume of the sound produced depends upon the amplitude of the oscillation. Accordingly, it is apparent that the greatest volume of sound for Jan electrcmagnet of the given strength will be produced when the period of oscillation of the armature, as induced by the electromagnet, cor

responds to the natural period of vibration of the armature as determined by the stiffness ofthe spider spring 3?. Accordingly, it is exceedingly important that the normal spacing between the armature M and the projection 56 be so fixed as to induce an oscillation of the armature having a period corresponding to'the natural period of oscillation. The structure above described is peare positioned in contact with each other face to face and hence are inherently spaced from each other a fixed distance. In addition to'the above, the adjusting screw 36, previously described, engages the extremity 48 of the finger 4'1 and is adapted to simultaneouslyadjust the normal position of both contact elements 5! and 58 with respect to the normal position of the armature. Since the movable contact element 41 is carried by the finger 49, adjustment of the latter by means of adjusting screws 30 adjusts the position of both of these members simultaneously without changing the pressure of contact between contact elements 51 and 58. The adjusting screw 30 performs the additional function of preventing follow-up movements of the finger 41 when the movable contact member 49 is deflected by the arma-. ture.

The amplitude of vibration of the armature and therefore the volume of the sound are also materially increased by two other novel features of the construction. The first of these is the cup shaped stamping which performs among others the important function of increasing the number of lines of flux and therefore the force exerted by the electromagnet on the armature. The second novel feature mentioned resides in'the construction of the armature supporting spider and particularly the provision of what may be termed a loose spoke in the spider. The spider construction, involving as it does, radial supporting spokes, insures proper alignment of the armature during oscillation, and the provision of one loose spoke materially increases the freedom of oscillation without destroying the guiding effect. In this connection it should be noted that if the spokes were all connected to the ring 38, the spokes would be placed under tension when they were deflected. Disconnecting one of the spokes from the ring enables it to slide in and out toward the axis as the armature oscillates, thereby relieving the tension which otherwise would resist oscillation.

All of these features contribute to increase the efiiciency of the horn, with the result that less electrical current is required to produce a given audible output.

The power unit described above is so designed that it may be readily adapted to a number of different diaphragm or casing assemblies. The

first of these assemblies is shown best in Figures 1 and 2 and comprises an assembly of the power unit in conjunction with a small diaphragm of substantially the same diameter as the casing J.

This small diaphragm assembly includes a cylin-' drical band 6% of sheet metal having an inturned flange BI at one end thereof. A flexible sheet metal diaphragm 62 is fitted within the band 60 and seats against the inturned flange 6| of the latter, and an annular spacer member 63' is pressed into the opposite end of the band 60 to lock the diaphragm'in position. When the diaphragm assembly is mounted upon the power unit, the bandfifi is. fitted over the peripheries of the casing flange l2 and theinterrupter and armature supports 36 and 31, as best shown in Figure 1, until the spacer 63 seats against the armature spider 31. Thereafter, the left hand endof the band 69 is spun inwardly over flange I2 of the casing If) to lock the parts in position. If desired, in place of a continuous spun flange 64, the band 60 may be provided with circumferentially spaced tongues which are. simply bent over the casing flange 82 to hold the parts in position. It is apparent that the diaphragm assembly secures the armature and interrupter mechanism in position and that the spacer 63 properly positions the diaphragm with respect to the armature. The

. diaphragm may just contact the projection 68' on the armature although a small clearance between these two members is preferable. As shown in Figure 4, the projections 13 and I3 on the casing flange l2 and the interrupter support 36. respectively, extend into a small slot 65 formed in band 60. This arrangement prevents relative rotation between the interrupter support and the casing.

It will be noted that the horn assembly described above is exceedingly simple and compact and can be readily assembled. While the diaphragm retaining flange BI is shown as a simple retaining flange, it is apparent that it may be given any desired form, to provide an ornamental front grille or the like for the diaphragm. While it is preferred to mount the armature upon spider 31 independently of the diaphragm 52, it is apparent that if desired the armature M may be mounted directly upon the diaphragm 62, in which event the spider 3! will be eliminated and the diaphragm positioned at the illustrated location of the armature spider. vIn this event, any suitable retaining ring similar to annular band 60 will be provided to secure the diaphragm and armature support in position.

In Fig. 6 the power unit is shown assembled in conjunction with a diaphragm of substantially larger diameter than the casing of the power unit. In this modification of the invention, the

power unit per se, including the casing theelectromagnet, the interrupter support 36, the armature support 3?, the armature MT, and the electrical circuits are identical to the structure shown and described in connection with Figures 1 to 5, inclusive. In this assembly, however, in place of the cylindrical band (ill shown in Figure 1, there is provided a stepped ring 80 having three axially spaced radially extending shoulders formed at 8!, 82, and 83, respectively. These shoulders are of progressively increasing diameter. Shoulder 8| is adapted to seat against the rear face of casing flange 52', which corresponds to the flange l2 shown in Figure 1, and the interrupter support 36' and armature spider 37' are fitted within the cylindrical portion-84 of ring'flll between shoulders BI and 82 and seat against the flange l2. Thereafter, an annular clamping vantage where, as m Figures 7 to 12. it is desired ring-85 having'a cylindrical flange 8% is pressed intothe cylindrical portion {it of ring St to lock the latter to the casing 58'. A relatively large flexible diaphragm 81 is then seated against the shoulder 83 of ring 81} and clamped thereto by means of a sheet metal cover plate 83. The cover plate 88 has a shoulder 89 adapted to seat against the periphery of the diaphragm and the margin of the cover plate is flanged over the shoulder 83 of ring 80 at fill to secure the diaphragm and cover plate in position. The cover plate may be of any desired configuration, but should be provided with asuitable opening for the egress of sound, such as the opening 9i.

It is apparent that the assembly of the improved power unit, in conjunction with a diaphragm of any desired size, may be accomplished by the means shown in Figure 6 without the necessity of any change whatsoever in the construction of the power unit itself. Preferably the power unit is made of extremely small size in order to increase its range of usefulness. It is found, however, that in spite of the small size of the power unit, it is possible to operate a relatively large diaphragm thereby, particularly if the spacing between the armature and the projection on the movable contact member is so determined as to induce a period of oscillation of the armature equal to the natural period of vvibration as determined by the. stiflness of the armature supporting spider.

In Figures 7 to 12 is shown the manner in which the improved power unit of this application may be utilized in conjunction with a lamp,

. wherein a horn and lamp are combined within a single casing. In this construction, the horn unit is provided with the small size diaphragm, the assembled power unit and diaphragm being identical in all respects to that shown in Figure 1. The use of the small size diaphragm is of adto mount the horn within a small torpedo shaped lamp casing of a size adapted for use on bicycles and the like.

Referring particularly to Figures 7 to 12, the casing for the combined horn and light is of generally torpedo shape and is formed of a pair of complementary sheet metal sections E03 and IIII. The lower section IilI is provided with an I embossed portion I02 by means of which it may be mounted upon a fender or other portion of a bicycle or the like.

Mounted within this casing is the complete horn unit shown in Figiue l of the drawings, in conjunction with a head light assembly structure. The light assembly comprises a substantially cylindrical sheet metal member I62 provided with three circumferentially spaced cut away portions or apertures Ills, Hi1, and HI, respectively, intermediate the ends of the cylinder. These apertures are separated by unbroken connecting portions H2, H3, and lid. Secured to the connecting portion H2 in any desired manner, such as by welding, is supporting bracket H6, shown best in Figure 9. This bracket is provided with a pair of apertured feet it? and H8 adapted to seat against the interior of the casing member NH; and bolts H9 are provided extending through suitable holes, not shown, in the casing member ill! and the apertures in the bracket feet Ill and H8 to fix the cylindrical member I08 in position in the casing. As shown in Figure 8, the bracket member i ll? may be provided with a bent over tongue lLZil, which extends through a suitable slot in the connecting por-- The forward or right hand end of the cylindrical member H38, as viewed in Figure 8, is provided with a lamp bulb support and reflector I22, comprising a semi-spherical sheet metal member having a rearwardly directed peripheral flange I24. Suitable tongues I25, formed on the flange I24, are adapted to engage in bayonet slots I26 in the cylindrical member I88 to secure the member I22 in position. A conventional lamp bulb I28 is threaded centrally into the spherical portion of member I 22.

At the opposite end of the cylindrical member I98, there is provided. a sheet metal attaching member, indicated generally at I38, and shown best in Figure 11. Member I30 is provided witha cylindrical portion I3 I- which is press fitted into the end of the cylindrical member H33 and is provided at one end with an outwardly extending flange I32 adapted to seat against the extremity of the cylindrical member W8; A plurality of circumferentially spaced tongues I33 extend axially-from' the periphery of flange I32 in telescoping relationship to the annular ring member E9 of the horn assembly and the extremities I3 3 of tongues I33 are bent inwardly and engage behind the flange or tongues 64' of ring member 553 to securely connect the horn structure and the lamp assembly.

Connecting element I30 described above is initially formed as a cup-shaped member, where upon portions of the bottom or" the cup are cut away to leave a diametrically extending web- I shown best in Figure 1. To this web is secured a spring contact strip I of generally U-shape, one side of the U-shaped spring contact strip being riveted to the web I35 by means of a rivet IN. A layer of insulating material I62 is positioned between the spring contact strip M8 and web I35 and a second insulating layer I 33 is provided between one head of the rivet I4! and the web I35 to completely insulate the spring contact strip I48 from the web. A terminal block I4 3 is secured in any desired manner to the contact strip Hill, as by brazing or otherwise, and a terminal screw I is provided in block IM to provide a means for attaching the non-grounded terminal Itt of the outside electrical circuit.

When the combined horn and light are assembled in the torpedo casing, a suitable lens Itll is secured to the open end of the casing by means or" a bezel [Si in the usual manner. As best shown in Figure 12, the casing is provided with a plurality of longitudinally extending slots I52, through which the sound from the horn may pass unimpeded.

It is apparent, in view of the above, that there is provided, in accordance with this form of the invention, an exceedingly simple combined horn and light of such small dimensions that it isreadily adapted for use in conjunction with a relatively small diameter torpedo shaped casing.

In practice, combined horn and light units of the type shown in Figures '7 to 12, inclusive, are manufactured in which the maximum diameter of the torpedo casing is approximately two inches. It is apparent, however, that the invention is equally applicable to larger size torpedo shaped horn and light units, such as the type utilized on automobiles. In such a case, the horn maybe provided with alarger size diaphragm, such as that shown in Fig. 6, and the cylindrical member over, it is apparent that the horn unit of the,

present invention embodies a number of improved characteristics, including a positive fixing of the relative spacing between the moving parts inde pendently of any variations in the size or distortation of the casing. The horn unit is ex ceedingly rugged, foolproof, and inexpensive to manufacture. j

While several forms of the invention have been shown and described, it is apparent that others are available within the spirit of the foregoing specification, the accompanying drawings, and within the scope of the appended claims. What is claimed is: v

1. In a horn assembly, a casing member open at one end, an electromagnet in said casing, means fixedly associated with said casing forming a shoulder facing the open end thereof, a circuit interrupter support seated against said shoulder, a flexible sheet metal member seated against said shoulder in overlapping relation to said support, an electromagnetic armature carried by said member, said armature being adapted to be attracted by said electromagnet, andan interrupter for the electromagnet circuit including a contact element and a flexible contact member independently secured to said support,

said flexible contact member having a portion,

normally in engagement with said contact element and having means projecting into the path of movement of the armature whereby movement of the armature toward the electromagnet effects separation of said portion and said contact element, and means for flexing a portion of said interrupter support for simultaneously adjusting the normal position of both said contacts toward or away from said armature.

2. In a horn assembly, a substantially cylindrical casing having an outwardly extending flange at one end, an electromagnet in said cas ing, a pair of flexible sheet metal members seated against said shoulder in overlapping relation, a circuit interrupter for said electromagnet carried by one of said sheet metal members, and an armature carried by the other member, means for securing said sheet metal members to said shoulder, and means for flexing the sheet metal member carrying said interrupter to adjust said interrupter.

3. A horn including a casing, an electromagnet in the casing, an armature movably carried by the casing and adapted to be operated by said electromagnet, said casing having an annular shoulder, a sheet metal member seated at its marginal portions against said shoulder and having its central portion cut away to receive said armature, said sheet metal member having an inwardly extending portion adapted to be flexed independently of said marginal portions,,a flexible contact member secured to but electrically insulated from said first mentioned member at the point of attachment, a contact portion on said flexible contact member normally in electrically conductive engagement with said inwardly extending portion of said sheet metal member, means on said flexible contact member projecting into the path of movement of said armature whereby movement of said armature towardjsaid electromagnet deflects said flexible contact member to eflect separation'of said contacts, and means for deflecting said inwardly extending portion of said sheet metal'member tosimultaneously adjust then'ormal position of both said contacting portions of said members toward and away'from said armature.

l. In a horn assembly, a casing member open at one end, an electromagnet in said casing, means fixedly associated with said casing forming a shoulder facing the open end thereof, 'a'circuit interrupter support seated against said shoulder, a flexible member' having radially extending arms seated against saidshoulder, an armature carried by said arms coaxially of and in prox imity to said electromagnet, a diaphragm assembly seated against said shoulder, said dia? phragm assembly including a diaphragm, means for holding said circuit interrupter support, said armature supporting member, and said dia phragm assembly against said shoulder in overlapping relation. 1 j

5. In a horn assembly, a casingmemberopen at one end, an electromagnet in said casing,

means fixedly associated with said casing forming,

a shoulder facing the open end thereof, a flexible circuit interrupter support seated against said shoulder, a flexible armature supporting member seated against said shoulder, a diaphragm assembly seated against said shoulder said diaphragm assembly including a diaphragm, means for holding said circuit interrupter support, said armature supporting member, and said diaphragm assembly against said shoulder in overlapping relation, an armature carried by said flexible armature supporting member and adapted to engage and vibrate said diaphragm, and

' an interrupter for the electromagnet circuit, in-

cluding a contact element and a movable contact member independently secured to said interrupter support, said movable contact member having a contact element normally in engagement with said first mentioned contact element, and said movable contact member having means projecting into the path of movementof the armature, I

whereby movement of the armature toward the electromagnet effects separation of said contact elements, and means for flexing said interrupter support for-adjusting the point of contact between said armature and said means on said movable contact member.

6. In a horn assembly, a substantially cylindrical casing having an outwardly extending flange at one end, an electromagnet in said casing, a pair of sheet metal members seated against said flange in overlapping relation, a circuit interrupter for said electromagnet carried by one of said sheet metal membersand an armature carried by the other member, and means for securing said sheet metal members to said flange, said last named means comprising a diaphragm assembly'including a diaphragm adapted to be operated by said armature.

' 7. In a horn a cup shaped casing member open at one end, an electromagnetic core piece in the casing member extending axially thereof and secured at one end to the opposite end wall .of said casing member, a disc of insulating material carried by the opposite end of said core, an electrical winding on the core between said disc and said end wall of the casing member, a tubular sheet metal spacer surrounding said coil between the disc and said end wall, means for securing a movable armature and a circuit interrupter mechanism each carried by said casing on the opposite side of said disc from said tubular member.

8. In a horn, a casing, an electromagnet in the casing, a flexible spider having a plurality of radially extending spokes, an armature carried at the hub of said spider, means for fixedly connecting certain of said spokes at their outer ends to the casing, and means for supporting and guiding the outer end of another spoke for movement toward and from said hub in the plane of said spider.

9. In a horn, a cup-shaped casing, an electromagnet having a winding substantially filling said casing, said winding and the said casing being co-axial, an armature resiliently supported adjacent the other end of said core, a current interrupter comprising a pair of arcuately shaped flexible fingers each extending through a substantial are around the armature in the annular space between the armature and the side wall of the casing in substantially the transverse plane of the armature and independently thereof, one end of each of said fingers being supported with respect to the casing and said fingers having their free end portions overlapped and normally in electrical contact with each other, and means for separating said contacts upon a predetermined movement of the armature towards said core.

10. In a horn, a cup-shaped casing, an electromagnet having a winding substantially filling said casing, said winding and the said casing being co-axial, an armature resiliently supported adjacent the other end of said core, a current interrupter comprising a pair of arcuately shaped resilient fingers extending through a substantial are around the armature in the annular space between the armature and the side wall of the casing in substantially the transverse plane of the armature and independently thereof, said fingers having free end portions overlapped and normally in electrical contact with each other, means on said armature for engaging one of said fingers and separating said contacts upon a predetermined movement of the armature towards said core, and means for deflecting both of said fingers simultaneously to adjust the point at which said means on the armature engages said one finger.

LEE M. WILEY. 

